Discrete element simulation of direct shear tests for investigating the influence of bedding dips on fracture propagation in carbonate-rich shale

doi:10.3969/j.issn.2096-1693.2025.03.024

Petroleum Science Bulletin ›› 2025, Vol. 10 ›› Issue (6): 1199-1214. doi: 10.3969/j.issn.2096-1693.2025.03.024

Discrete element simulation of direct shear tests for investigating the influence of bedding dips on fracture propagation in carbonate-rich shale

LI Junliang¹^,², ZHANG Kuihua²^,³, FENG Haifeng⁴, LIU Xinjin¹^,², LIU Zhina⁴^,^*(), QIN Feng¹^,², CHEN Tao¹^,², WANG Yong¹^,², YAN Jiajie⁴, YUAN Guiting¹^,², YU Fusheng⁴, WEI Xiaoliang¹^,⁵

1 Exploration and Development Research Institute, Sinopec Shengli Oilfield Company, Dongying 257015, China
2 National Key Laboratory of Shale Oil and Gas Enrichment Mechanism and Efficient Development, Dongying 257015, China
3 Sinopec Shengli Oilfield Company, Dongying 257000, China
4 College of Geosciences, China University of Petroleum, Beijing 102249, China
5 Sinopec Shengli Oilfield Postdoctoral Workstation, Dongying 257015, China

Received:2025-06-05 Revised:2025-09-17 Online:2025-12-30 Published:2025-12-30
Contact: LIU Zhina E-mail:zhina.liu@cup.edu.cn

层理倾角对富碳酸盐页岩裂缝扩展规律影响的直剪试验离散元模拟

李军亮¹^,², 张奎华²^,³, 冯海风⁴, 刘鑫金¹^,², 刘志娜⁴^,^*(), 秦峰¹^,², 陈涛¹^,², 王勇¹^,², 闫嘉杰⁴, 苑贵亭¹^,², 于福生⁴, 魏晓亮¹^,⁵

1 中国石化胜利油田分公司勘探开发研究院，东营 257015
2 页岩油气富集机理与高效开发全国重点实验室，东营 257015
3 中国石化胜利油田分公司，东营 257000
4 中国石油大学(北京)地球科学学院，北京 102249
5 中石化胜利油田博士后工作站，东营 257015

通讯作者: 刘志娜 E-mail:zhina.liu@cup.edu.cn
作者简介:李军亮(1975年—)，博士研究生，主要研究方向为页岩油地质综合研究工作，lijunliang.slyt@sinopec.com。
基金资助:
国家科技重大专项“渤海湾盆地济阳坳陷古近系陆相页岩油勘探开发技术与集成示范”(2024ZD1405100);国家自然科学基金企业创新发展联合基金项目(U24B6002);中国石油化工集团有限公司项目(P23084);中国石油化工集团有限公司项目(P24027)

Abstract

Abstract:

This study focuses on the carbonate-rich shale of the lower Sha-3 to upper Sha-4 sub-members in the Dongying Sag of the Jiyang Depression within the Bohai Bay Basin. Based on the discrete element simulation and acoustic emission monitoring test methods, a numerical model for shale direct shear tests was constructed. The study systematically revealed the crack propagation laws and energy evolution characteristics under different bedding dip angles, and established a quantitative relationship between bedding dip angle, stress state, and the number of micro-fractures. The research results show that: (1) During direct shearing, high shear stress induces en echelon tensile fractures with an approximate 45° angle. After expansion, these fractures connect with shear fractures developed along the bedding to form a macroscopic fracture zone. As the bedding dip angle increases, the fracture zone gradually transitions from a stepped shape to a “zigzag” shape, exhibiting significant heterogeneity. (2) The shale fracture mechanism is dependent on the bedding dip angle: under low dip angles, shear fracture along the bedding is dominant; as the dip angle increases, the dominant fracture mechanism gradually shifts to matrix tensile-shear composite fracture. (3) The initiation stress of fractures is relatively low, and its variation with the bedding dip angle is not obvious; however, the damage stress and peak stress of fractures increase first and then decrease with the increase of the dip angle, reaching their peaks within the range of 40° to 50°. (4) Based on acoustic emission monitoring, it is found that crack propagation can be divided into three stages: initiation, rapid expansion (contributing 85% of the total number of cracks), and slow expansion. Tensile cracks account for 82.6%, while shear cracks (accounting for 17.4%) are mainly distributed along the bedding. (5) A comprehensive comparison of numerical simulation results, shale core fracture characteristics, and laboratory direct shear test results reveals similar fracture propagation laws, including shear fractures developed along the bedding plane and tensile fractures that obliquely cut (or penetrate) the bedding. The bedding dip angle is a key factor controlling the shale fracture development pattern, directly affecting the fracture propagation direction, complexity, and reconstruction volume. The findings of this study provide a theoretical basis for explaining the genetic mechanism and development pattern of natural fractures in continental shales, and also offer scientific support for the prediction of natural fractures in shale oil and gas exploration and development, which is of great significance for improving shale oil recovery efficiency and ensuring operational safety.

Key words: discrete element method, acoustic emission, shale, crack propagation, fracture mechanism

摘要：

本研究针对渤海湾盆地济阳坳陷东营凹陷沙三下-沙四上亚段富碳酸盐质页岩，结合离散元模拟与声发射监测方法，构建直剪试验数值模型，分析不同层理倾角下的裂纹扩展规律和能量演化特征，建立层理倾角、应力状态与裂缝数量的定量关系。结果表明：(1)直剪作用下，高剪应力诱发约45°雁列状张裂缝，扩展后与沿层理剪切裂隙贯通，形成宏观破裂带；随层理倾角增大，破裂带由阶梯状转为“之”字形，非均质性增强；(2)破裂机制受层理倾角控制，低角度以沿层剪切为主，高角度转为基质张-剪复合破裂；(3)起裂、损伤和峰值应力随倾角增大先升后降，在40°~50°达到最大；(4)裂纹扩展分为起裂、快速扩展(占85%以上)和慢速扩展三阶段，张裂纹占82.6%，剪裂纹占17.4%且多沿层理分布；(5)数值模拟、岩芯观察与室内试验均显示相似扩展模式，包括沿层剪裂隙和斜切或穿层张裂隙。层理倾角是控制裂缝发育的关键因素，直接影响裂缝方向、复杂程度和改造体积。研究成果为陆相页岩天然裂缝的成因与预测提供理论支持，对提升页岩油开采效率和作业安全具有重要意义。

关键词: 离散元, 声发射, 页岩, 裂纹扩展, 破裂机制

CLC Number:

LI Junliang, ZHANG Kuihua, FENG Haifeng, LIU Xinjin, LIU Zhina, QIN Feng, CHEN Tao, WANG Yong, YAN Jiajie, YUAN Guiting, YU Fusheng, WEI Xiaoliang. Discrete element simulation of direct shear tests for investigating the influence of bedding dips on fracture propagation in carbonate-rich shale[J]. Petroleum Science Bulletin, 2025, 10(6): 1199-1214.

李军亮, 张奎华, 冯海风, 刘鑫金, 刘志娜, 秦峰, 陈涛, 王勇, 闫嘉杰, 苑贵亭, 于福生, 魏晓亮. 层理倾角对富碳酸盐页岩裂缝扩展规律影响的直剪试验离散元模拟[J]. 石油科学通报, 2025, 10(6): 1199-1214.

/ / Recommend / Download Citations

URL: https://sykxtb.cup.edu.cn/EN/10.3969/j.issn.2096-1693.2025.03.024

https://sykxtb.cup.edu.cn/EN/Y2025/V10/I6/1199

Figures/Tables 13

Fig. 1 Particle flow model of direct shear test

Table 1 Microscopic parameters of the particle flow model

属性	页岩	层理面
线性接触模量/GPa	3	1
线性接触法/切向刚度比	1.5	1.5
线性接触颗粒摩擦系数	0.2	0.2
平行粘结模量/GPa	3	1
平行粘结法/切向刚度比	1.5	1.5
平行粘结抗拉强度/MPa	20	6
平行粘结粘聚力/MPa	60	6
平行粘结内摩擦角/°	40	35

Fig. 2 Comparison of shear stress-shear displacement curves between physical experiments and particle flow models

Fig. 3 Comparison of cumulative acoustic emission counts versus shear displacement in physical experiments and particle flow models

Fig. 4 Comparison of fracture propagation laws in shales

Fig. 5 Results of shear failure surface in particle flow models (DZ group)

Fig. 6 Distribution of microcracks in particle flow models (DZ group)

Fig. 7 Shear displacement in particle flow models (DZ group)

Fig. 8 Curve of cumulative acoustic emission counts in DZ group with the increase of shear displacement

Fig. 9 Three key mechanical thresholds varying with the bedding dip angle

Fig. 10 Curve of the number of microcracks varying with shear displacement

Fig. 11 Comparison of the number of microcracks in the model with the variation of bedding dips (The squares in the Fig. represent the total number of cracks, triangles represent tensile cracks, and circles represent shear cracks)

Fig. 12 Comparison of SJ series and DZ series models

References 36

[1]	KENETI S. W. Shear behavior of the montney shale under double-shear test. 45th US Rock Mechanics Geomechanics Symposium[C]. San Francisco：American Rock Mechanics Association, 2011.
[2]	HENG S, GUO Y, YANG C, et al. Experimental and theoretical study of the anisotropic properties of shale[J]. International Journal of Rock Mechanics and Mining Sciences, 2015, 74: 58-68. doi: 10.1016/j.ijrmms.2015.01.003 URL
[3]	朱颖. 油页岩层理对其力学特性及裂缝起裂与扩展的影响研究[D]. 吉林: 吉林大学, 2022.
	[ZHU Y. Study on the influence of oil shale bedding on its mechanical properties and fracture initiation and propagation[D]. Jilin: Jilin University, 2022.]
[4]	马天寿, 陈平. 层理页岩水平井井周剪切失稳区域预测方法[J]. 石油钻探技术, 2014, 42(5): 26-36.
	[MA T S, CHEN P. Prediction method of shear instability region around the borehole for horizontal wells in bedding shale[J]. Petroleum Drilling Techniques, 2014, 42(5): 26-36.]
[5]	袁和义, 陈平. 基于直剪试验的页岩水化作用的强度弱化规律[J]. 天然气工业, 2015, 35(11): 71-77.
	[YUAN H Y, CHEN P. Strength weakening rules of shale hydration based on direct shear tests[J]. Nat Gas Ind, 2015, 35(11): 71-77.]
[6]	LU H J, XIE H P, LUO Y, et al. Failure characterization of Longmaxi shale under direct shear mode loadings[J]. International Journal of Rock Mechanics and Mining Sciences, 2021, 148.
[7]	ZHANG A, ZHANG R, LU H, et al. Anisotropy in shear failure of shale: An insight from microcracking to macrorupture[J]. Measurement, 2025, 243116391-116391.
[8]	ZHENG B, QI S, GUO S, et al. Experimental study of direct shear properties of anisotropic reservoir shale[J]. Energies, 2024, 17(8): 1977-1996. doi: 10.3390/en17081977 URL
[9]	FAN Z D, XIE H P, REN L, et al. Anisotropy in shear-sliding fracture behavior of layered shale under different normal stress conditions[J]. Journal of Central South University, 2022, 29(11): 3678-3694. doi: 10.1007/s11771-022-5156-9
[10]	XIE Y, HOU Z M, LIU H, et al. Anisotropic time-dependent behaviors of shale under direct shearing and associated empirical creep models[J]. Journal of Rock Mechanics and Geotechnical Engineering, 2024, 16(4): 1262-1279. doi: 10.1016/j.jrmge.2023.05.001 URL
[11]	张清照, 沈明荣, 丁文其. 结构面在剪切状态下的力学特性研究[J]. 水文地质工程地质, 2012, 39(2): 37-42.
	[ZHANG Q Z, SHEN M R, DING W Q, et al. Study on the mechanical properties of rock mass discontinuity under shear condition[J]. Hydrogeology and Engineering Geology, 2012, 39(2): 37-42.]
[12]	李存宝, 谢和平, 谢凌志. 页岩起裂应力和裂纹损伤应力的试验及理论[J]. 煤炭学报, 2017, 42(4): 969-976.
	[LI C B, XIE H P, XIE L Z. Experimental and theoretical study on the shale crack initiation stress and crack damage stress[J]. Journal of China Coal Society, 2017, 42(4): 969-976.]
[13]	衡帅, 李贤忠, 刘晓, 等. 直剪条件下页岩裂缝扩展演化机制研究[J]. 岩石力学与工程学报, 2019, 38(12): 2438-2450.
	[HENG S, LI X Z, LIU X, et al. Study on the propagation mechanisms of shale fractures under direct shear conditions[J]. Chinese Journal of Rock Mechanics and Engineering, 2019, 38(12): 2438-2450.]
[14]	刘先珊, 李涛, 张立君, 等. 储层页岩直剪破断特性及细观演化机制[J]. 中国石油大学学报(自然科学版), 2022, 46(5): 141-152.
	[LIU X S, LI T, ZHANG L J, et al. Characteristics of shear fracturing and corresponding evolution mechanism at micro-scale in direct shear tests for reservoir shale[J]. Journal of China University of Petroleum (Edition of Natural Science), 2022, 46(5): 141-152.]
[15]	YE C F, XIE H P, WU F, et al. Asymmetric failure mechanisms of anisotropic shale under direct shear[J]. International Journal of Rock Mechanics and Mining Sciences, 2024, 183: 105941-105958. doi: 10.1016/j.ijrmms.2024.105941 URL
[16]	叶春烽, 谢和平, 李存宝. 直接剪切下页岩的各向异性破坏特征和强度预测模型[J]. 工程科学与技术, 2024, 56(2): 257-267.
	[YE C F, XIE H P, LI C B. Anisotropic failure characteristics and strength prediction model of shale under direct shear[J]. Advanced Engineering Sciences, 2024, 56(2): 257-267.]
[17]	NI Q, POWRIE W, ZHANG X, et al. Effect of particle properties on soil behavior: 3-D numerical modeling of shear box tests[C]. San Francisco: American Rock Mechanics Association, 2000.
[18]	刘顺桂, 刘海宁, 王思敬, 等. 断续节理直剪试验与PFC-2D数值模拟分析[J]. 岩石力学与工程学报, 2008, (9): 1828-1836.
	[LIU S G, LIU H N, WANG S J, et al. Direct shear tests and PFC2D numerical simulation of intermittent joints[J]. Chinese Journal of Rock Mechanics and Engineering, 2008, (9): 1828-1836.]
[19]	LIU S H. Simulating a direct shear box test by DEM[J]. Canadian Geotechnical Journal, 2011, 43(2): 155-168. doi: 10.1139/t05-097 URL
[20]	LIU L W, LI H B, CHEN S H, et al. Effects of bedding planes on mechanical characteristics and crack evolution of rocks containing a single pre-existing flaw[J]. Engineering Geology, 2021, 293.
[21]	曹日红, 曹平, 林杭, 等. 不同粗糙度的节理直剪颗粒流分析[J]. 岩土力学, 2013, 34(s2): 456-463.
	[CAO R H, CAO P, LIN H, et al. Particle flow analysis of direct shear tests on joints with different roughnesses[J]. Rock and Soil Mechanics, 2013, 34(s2): 456-463.]
[22]	曹凯, 刘远明. 节理岩体剪切力学行为细观模拟分析[J]. 中国水运, 2018, (9): 72-74.
	[CAO K, LIU Y M. Mesoscopic simulation analysis of shear mechanical behavior of jointed rock masses[J]. China Water Transport, 2018, (9): 72-74.]
[23]	顾问, 丁伟, 施威, 等. 含软弱夹层岩体的剪切变形及破坏机理研究[J]. 河南科学, 2022, 40(8): 1229-1236.
	[GU W, DING W, SHI W, et al. Shear deformation and failure mechanism of rock mass with weak interlayer[J]. Henan Science, 2022, 40(8): 1229-1236.]
[24]	雷瑞德, 粟罗, 胡超, 等. 基于矿物颗粒模型的裂隙煤岩微裂纹扩展演化规律研究[J]. 煤矿安全, 2024, 55(11): 154-165.
	[LEI R D, SU L, HU C, et al. Study on the evolution law of microcrack propagation in fractured coal-rock based on mineral particle model[J]. Safety in Coal Mines, 2024, 55(11): 154-165.]
[25]	黄丹, 肖子龙, 汤文, 等. 不同开度节理大理岩破裂过程与断裂面形貌特征研究[J]. 工程地质学报, 2024, 32(6): 2239-2249.
	[HUANG D, XIAO Z L, TANG W, et al. Study on fracture process and fracture surface morphology characteristics of marble with different joint openings[J]. Journal of Engineering Geology, 2024, 32(6): 2239-2249.]
[26]	FAN Z, ZHOU Q, NIE X, et al. 3D anisotropic microcracking mechanisms of shale subjected to direct shear loading: A numerical insight[J]. Engineering Fracture Mechanics, 2024, 298: 109950-109966. doi: 10.1016/j.engfracmech.2024.109950 URL
[27]	WANG Z X, PENG J, KWOK C F, et al. Numerical simulation of failure and micro-cracking behavior of non-persistent rock joint under direct shear[J]. Engineering Geology, 2024, 342: 107760-107778. doi: 10.1016/j.enggeo.2024.107760 URL
[28]	LI B, LI Q. Coupled FEM-DEM modeling of permeability evolution in rough fractured shale during shearing under varying confining pressures[J]. Journal of Rock Mechanics and Geotechnical Engineering, 2025.
[29]	HOU C C, KANG Y S, LIU B, et al. Numerical investigation on shear mechanical characteristics of rock joints filled with clay-rich fillings[J]. Engineering Analysis with Boundary Elements, 2025, 178: 106303-106317. doi: 10.1016/j.enganabound.2025.106303 URL
[30]	POTYONDY DO. The bonded-particle model as a tool for rock mechanics research and application: current trends and future directions[J]. Geosystem Engineering, 2015, 18(1): 1-28. doi: 10.1080/12269328.2014.998346 URL
[31]	HAZZARD J F, YOUNG R P. Moment tensors and micromechanical models[J]. Tectonophysics, 2002, 356(1): 181-197. doi: 10.1016/S0040-1951(02)00384-0 URL
[32]	刘祥鑫, 张艳博, 梁正召, 等. 岩石破裂失稳声发射监测频段信息识别研究[J]. 岩土工程学报, 2017, 39(6): 1096-1105.
	[LIU X X, ZHANG Y B, et al. Recognition of frequency information in acoustic emission monitoring of rock fracture[J]. Chinese Journal of Geotechnical Engineering, 2017, 39(6): 1096-1105.]
[33]	刘建锋. 岩石声发射研究现状[J]. 四川师范大学学报(自然科学版), 2021, 44(5): 569-575.
	[LIU J F. Research status of rock acoustic emission[J]. Journal of Sichuan Normal University (Natural Science), 2021, 44(5): 569-575.]
[34]	李玉山, 席伟, 张诏飞, 等. 岩石蠕变声发射特性研究现状与展望[J]. 甘肃地质, 2021, 30(2): 66-69.
	[LI Y S, XI W, ZHANG Z F, et al. Research status and prospect of acoustic emission characteristics of rock creep[J]. Gansu Geology, 2021, 30(2): 66-69.]
[35]	ZHAI M Y, XUE L, FENG C B, et al. Effects of bedding planes on progressive failure of shales under uniaxial compression: Insights from acoustic emission characteristics[J]. Theoretical and Applied Fracture Mechanics, 2022, 119.
[36]	POTYONDY D O, CUNDALL P A. A bonded-particle model for fock[J]. International Journal of Rock Mechanics and Mining Sciences, 2004, (41): 1329-1364.

Please choose a citation manager

Content to export